iButtons.....Yea or Nea??

[Flyrod]

I have a temperature monitoring task that would be perfect for the iButton doodads. I know Dan C. has tried them, but I do not know the final verdict. Are these doodads worth a flip? Do they accurately give you the temp vs. time data we all hunger for? Any major shortfalls? How about it all you iButton beta testers?? is this a new religion or just vaporware in hard form?

[Paul Eastham]

Originally Posted by Flyrod

I have a temperature monitoring task that would be perfect for the iButton doodads. I know Dan C. has tried them, but I do not know the final verdict. Are these doodads worth a flip? Do they accurately give you the temp vs. time data we all hunger for? Any major shortfalls? How about it all you iButton beta testers?? is this a new religion or just vaporware in hard form?

I have used them, not in an airplane, but in my house, and found them to be reliable and accurate at temps 30-120F. .1 degree F resolution, 1-2 second polling frequency.

Hmm, I forgot I still had those...might be interesting to measure some temps FWF. I've also got some unused general purpose inputs on my Dynon EMS, but not sure what sort of sensor would be appropriate...

[GrayHawk]

Most of the 1-wire temperature sensors will only measure temperatures from ?55?C to +125?C (?67?F to +257?F), with 0.5 C accuracy from ?10?C to +85?C.

Is this going to be a wide enough range?

Also the interface is a digital interface vs. analog. Do you need real time display of values or just data logging?

[dan]

It was a humungous waste of time. The company wasn't willing to sell me individual units. They told me that they only sell in quantity. But...they said if I requested a "sample" that they would send me one. I requested one and it never showed up. WhatEVER.

[GrayHawk]

Originally Posted by dan

It was a humungous waste of time. The company wasn't willing to sell me individual units. They told me that they only sell in quantity. But...they said if I requested a "sample" that they would send me one. I requested one and it never showed up. WhatEVER.

The 'guts' of the iButton devices are generally 1-wire ICs made by Maxim Semiconductor and there are many places you can buy small quantities of these. I have used their temperature sensors (18S20) but mostly for home use or weather station. As I mentioned earlier the temperature range only goes up to 275F or so. The interface to a laptop for the 1-wire network (multiple temp. sensors on a single bus) can be as simple as a USB dongle and there are various programs around to read & log the temperatures.

[Flyrod]

Grayhawk,

I will be using them for checking avionics temps in the cockpit and behind the baggage locker. I have had trouble with two units in my aft space behind the baggage locker early this Summer and I want to see if the units are getting above the 160F operating spec. The trouble only comes about on second flights of hot days. I thought taping one off these buttons to the side of a unit would provide a good log of operating temps reached.

Where can you get the small quantities?

[GrayHawk]

I agree that if logging is all you want, an iButton temperature logger would be the simplist approach (no wire, just tape it on). There are enough people playing with these, that there ought to be a place to get small quantities. Maybe try http://www.ibuttonlink.com/

As for the 1-wired network and real time data, don't have a good example for aircraft but a good example of a home monitoring system is at http://www.welserver.com/index.htm

PS: As long as there is interest in temperature sensors, I also found this source which has a Type K Thermocouple, glass braid insulation, -454 to +2501F, which should survive FWF, for measurement of higher temperatures in odd places.
http://www.sparkfun.com/commerce/pro...roducts_id=251